If you’re looking for a dessert that celebrates rhubarb in the most irresistible way, Rhubarb Crumble Bars are it. With a buttery shortbread base, a juicy rhubarb filling, and a golden oat crumble topping, these bars strike that perfect balance of sweet and tart with every bite. They’re rustic, simple to make, and slice up beautifully for school snacks, potlucks, picnics, or just a cozy afternoon treat at home.
What I love most about these bars is how forgiving and family-friendly they are. The base and topping come from the same mixture, so you’re not making three different components from scratch. The filling is easy—just chopped rhubarb, a touch of sugar, and a little thickener to bring it all together. If you have older kids, they’ll enjoy measuring and mixing. Little ones can help press the crust into the pan or sprinkle on the crumble topping. It’s a great intro to baking with seasonal produce and the kind of recipe that brings everyone into the kitchen.
These bars are also perfect for those just discovering rhubarb. The tartness mellows in the oven, and the sweet crumble offers the right contrast to make every bite feel balanced and craveable. If you’ve got rhubarb in your garden or found some at the market, make these bars—they never last long in our house.
What You’ll Need
For the Crust and Crumble:
- 1½ cups all-purpose flour
- 1½ cups old-fashioned rolled oats
- ¾ cup brown sugar, packed
- ½ teaspoon baking soda
- ½ teaspoon salt
- ¾ cup unsalted butter, melted
- 1 teaspoon vanilla extract
For the Rhubarb Filling:
- 3 cups chopped rhubarb
- ½ cup granulated sugar
- 1 tablespoon cornstarch
- 1 tablespoon lemon juice
- Zest of ½ lemon (optional)
Pro Tips
- Cut rhubarb into small, even pieces so it cooks down evenly in the filling.
- Line your baking pan with parchment paper to make it easy to lift and slice the bars cleanly.
- Press the crust down firmly—use the bottom of a measuring cup for a nice, even layer.
- Cool completely before cutting for the neatest slices. The filling sets as it cools.
- Double the batch and bake in a 9×13 pan if you’re feeding a crowd.
Tools You’ll Need
- Mixing bowls (2)
- Measuring cups and spoons
- 8×8-inch baking pan
- Parchment paper
- Rubber spatula
- Knife for slicing
- Cooling rack
Substitutions & Variations
Gluten-Free: Use a 1:1 gluten-free flour blend and certified gluten-free oats.
Add Strawberries: Replace 1 cup of rhubarb with chopped strawberries for a classic twist.
Make it Vegan: Use vegan butter or coconut oil in place of regular butter.
Add Warm Spices: A pinch of cinnamon or ginger in the crumble pairs beautifully with rhubarb.
Sweeter Option: If your family prefers less tartness, increase the sugar in the filling to ¾ cup.
Make-Ahead Tips
- The crust/crumble mixture can be made ahead and stored in the fridge for up to 2 days.
- Rhubarb filling can be prepped and refrigerated for up to 1 day before baking.
- Baked bars freeze beautifully. Wrap tightly and freeze for up to 2 months.
How to Make Rhubarb Crumble Bars
Step 1: Preheat Oven and Prep Pan
Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving a bit of overhang on the sides.
Step 2: Make the Crust and Crumble
In a large bowl, combine the flour, oats, brown sugar, baking soda, and salt. Stir in the melted butter and vanilla until mixture forms moist crumbs.
Step 3: Press the Crust
Press two-thirds of the crumble mixture firmly into the bottom of the lined pan to form the crust.
Step 4: Prepare the Rhubarb Filling
In a separate bowl, toss chopped rhubarb with sugar, cornstarch, lemon juice, and zest. Mix until the rhubarb is evenly coated.
Step 5: Assemble the Bars
Spread the rhubarb filling evenly over the crust. Sprinkle the remaining crumble mixture over the top.
Step 6: Bake
Bake for 35–40 minutes or until the top is golden and the filling is bubbling around the edges. Cool completely in the pan.
Step 7: Slice and Serve
Use the parchment overhang to lift the bars from the pan. Slice into squares and serve at room temperature.
Leftovers & Storage
- Store bars in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days.
- To freeze, wrap individual bars in plastic wrap and place in a freezer-safe bag for up to 2 months.
- Thaw at room temperature or warm in a low oven for 10 minutes for a fresh-baked taste.
Final Thoughts
Rhubarb crumble bars are the kind of dessert that feels a little nostalgic and a lot delicious. They’re easy enough for a weekday bake but pretty enough for a special occasion. With their sweet, tangy filling and buttery crumble top, they capture everything that makes rhubarb special. Whether you’re baking for your family or sharing with neighbors, this is a recipe that brings people together. If you make them, let me know how they turned out—your comments always make my day.